Fuel pump

ABSTRACT

There is provided a fuel pump ( 10 ) which includes an impeller ( 20 ) in a disk-like shape; a casing ( 18 ) comprised of a pump cover ( 14 ) and a pump body ( 16 ) that rotatably accommodate the impeller; and a motor section ( 70 ) that drives to rotate the impeller; wherein, on at least one of seal portions of the casing ( 18 ) and in its place facing to a series of recesses ( 20   b,   20   c ) of the impeller, a recessed shape ( 35,36 ) in a micron order is formed in expectation of a swelling amount of the series of recesses ( 20   b,   20   c ) of the impeller ( 20 ).

TECHNICAL FIELD

This invention relates to a fuel pump, and in detail, relates to a fuel pump having an impeller and a pump casing that rotatably accommodates the impeller.

BACKGROUND ART

Fuel pumps are known as devices for supplying a fuel in a fuel tank to an internal combustion engine (for example, a vehicle engine etc.). The fuel pumps of this type generally have a pump section. The pump section includes a casing and an impeller in a nearly disc-like shape that is rotatably accommodated in the casing. On a surface of the impeller facing to a fuel suction side, a blade groove portion is circularly formed along the outer periphery of the impeller. On a surface of the impeller facing to a fuel discharge side, another blade groove portion is formed at a place corresponding to the blade groove portion formed at the suction side of the impeller. These groove portions formed on the surfaces at the suction side and at the discharge side of the impeller, are communicated with each other through their bottoms.

On respective inner faces of the casing that are facing to the suction side and the discharge side of the impeller, pump passage are formed each extending from an upstream end to a downstream end along a rotating direction of the impeller in a region corresponding to each blade groove portion formed on the impeller. The upstream end of the suction-side pump passage is communicated with the outside of the casing through a fuel suction opening, and the downstream end of the discharge-side pump passage is communicated with the outside of the casing through a fuel discharge opening.

In the fuel pumps thus configured, upon rotation of the impeller, the fuel is sucked in the pump casing through the suction opening and the sucked fuel is introduced into the blade groove portions of the impeller and the pump passages. A centrifugal force due to rotation of the impeller acts on the fuel sucked in the pump casing. The fuel sucked in the pump casing flows along the pump passages to the downstream side thereof while being pressurized by the centrifugal force of the impeller, and is then discharged to the outside of the pump casing from the discharge opening.

In such fuel pumps, in order to prevent a reduction in discharge efficiency of the pump due to a leakage loss emerging through a clearance in contact with the surface of the impeller and between the surface and a slidable face of a pump cover or a pump base, clearances in the thrust direction are made extremely small. Thus, when the fuel pressure in a pump chamber is increasing toward the pump chamber outlet from the fuel suction opening by the rotation of the blade groove portions, the impeller rotates while making contact with a place of the pump casing facing to the pump chamber outlet because of unbalanced pressure between at around the pump chamber outlet in the pump casing and at around the fuel suction opening in the pump casing.

Thus, in order to prevent such a contact, it is known to form, near the outlet of the pump on the slidable face of the pump casing, a larger clearance than the small clearance between the surface of the impeller and the pump casing, to thereby make a slipping portion (see, for example, Patent Document 1).

CITATION LIST Patent Document

-   Patent Document 1: Japanese Patent Application Laid-open No.     H05(1993)-187382

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

According to the experiment and investigation by the inventor, it has been confirmed that a dimensional deformation of the impeller occurs significantly at a series of recesses thereof. Thus, in order to prevent the contact between the pump casing and the impeller, it is hard to say that it is fully enough to provide only the slipping portion shown in Patent Document 1.

This invention has been made in consideration of the above situation, and an object thereof is to provide a fuel pump that has a simple and low cost configuration, and that prevents increase in rotational resistance of the impeller and occurrence of trouble in the pump chamber, such as locking, to thereby achieve both ensuring the reliability and keeping the pump performance.

Means for Solving the Problems

A fuel pump according to the invention is configured to include: an impeller in a disc-like shape; a casing comprising a pump cover and a pump body that rotatably accommodate the impeller; and a motor section that drives to rotate the impeller; wherein, on each of front and back faces of the impeller, a series of recesses being repeated in a circumferential direction is formed in a region that extends along the circumferential direction with a given distance apart inside from an outer periphery; wherein, on the pump cover facing to the front face of the impeller, a first groove is formed that extends in a region facing to the series of recesses of the impeller, from an upstream end to a downstream end; wherein, on the pump body facing to the back face of the impeller, a second groove is formed that extends in a region facing to the other series of recesses of the impeller, from an upstream end to a downstream end; wherein, in the casing, there are formed a fuel discharge opening that communicates between near the downstream end of the first groove and an outside of the casing, and a fuel suction opening that communicates between near the upstream end of the second groove and an outside of the casing; and wherein, seal portions are provided, as viewed in a rotating direction of the impeller, between the upstream end and the downstream end of the first groove on the pump cover and between the upstream end and the downstream end of the pump body, respectively; said fuel pump comprising, on at least one of the seal portions of the casing and in its place facing to the series of recesses of the impeller, a recessed shape in a micron order formed in expectation of a swelling amount of said series of recesses of the impeller.

Effect of the Invention

According to the fuel pump of the invention, it is possible to provide a fuel pump that has a simple and low cost configuration, and that prevents increase in rotational resistance of the impeller and occurrence of trouble in the pump chamber, such as locking, to thereby achieve both ensuring the reliability and keeping the pump performance.

The foregoing and other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the embodiment and the illustration of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view showing a whole configuration of a fuel pump of Embodiment 1 of the invention.

FIG. 2 is a enlarged longitudinal cross-sectional view of a pump section shown in FIG. 1.

FIG. 3 is a top view of an impeller according to Embodiment 1 of the invention.

FIG. 4 is a top view of a pump body, viewed from the side of the impeller, according to Embodiment 1 of the invention.

FIG. 5 is a top view of a pump cover, viewed from the side of the impeller, according to Embodiment 1 of the invention.

FIG. 6 is a partial cross-sectional view of the pump section 12 according to Embodiment 1 of the invention.

MODES FOR CARRYING OUT THE INVENTION Embodiment 1

Embodiment 1 of the invention will be described with reference to FIG. 1 through FIG. 6. Note that, in the respective figures, the same symbols represent the same or equivalent parts.

What is characterized by the invention is summarized that, on a seal portion that is provided on an inner slidable face of a casing facing to a series of blade grooves of an impeller, from a fuel discharge opening to a fuel suction opening as viewed in a rotating direction, a recessed shape along a nearly circular circumference is formed that is resulted from further broadening a clearance by a micron order.

FIG. 1 is a longitudinal cross-sectional view showing a whole configuration of a fuel pump of Embodiment 1 of the invention. As shown in FIG. 1, the fuel pump 10 is configured with a motor section 70 and a pump section 12.

The motor section 70 is provided with a housing 72, a motor cover 73, magnets 74,75, and a rotor 76. The housing 72 is formed in a nearly cylindrical shape. The motor cover 73 is fixed to the housing 72 by caulking inwardly an upper end 72 a of the housing 72 (up and down in FIG. 1 correspond to up and down of the fuel pump 10, here). On the motor cover 73, a discharge port 73 a is formed that is open upward. The magnets 74,75 are fixed to an inner wall of the housing 72. The rotor 76 has a main body 77 composed of a laminated core and a coil, etc., and a shaft 78 penetrating up and down through the main body 77. An upper end portion 78 a of the shaft 78 is rotatably mounted to the motor cover 73 byway of a bearing 81. A lower end portion 78 b of the shaft 78 is rotatably mounted to a pump cover 14 of the pump section 12 by way of a bearing 82. Regarding the motor section 70, since its configuration is similar to that of the conventional fuel pump, a more detailed description thereof is omitted here.

FIG. 2 shows a selectively enlarged view of the pump section shown in FIG. 1.

The pump section 12 is provided with a casing 18 and an impeller 20.

As shown in FIG. 3, the impeller 20 is nearly in a disc-like shape. On a fuel-suction-side face of the impeller 20, a first series of blade grooves 20 b successively arranged in a circumference direction is formed circularly with a given distance apart from an outer periphery face 20 e. That is, the first series of blade grooves 20 b is apart from the outer periphery face 20 e of the impeller 20 by an outer periphery wall 20 d of the impeller 20. On a fuel-discharge-side face of the impeller 20, a second series of blade grooves 20 c successively arranged in a circumference direction is formed circularly in a place corresponding to the first series of blade grooves 20 b formed on the fuel-suction-side face of the impeller 20 (that is, in a region being apart by a given distance from the outer periphery face 20 e). Note that the bottoms of the first series of blade grooves 20 b and the second series of blade grooves 20 c are communicated with each other through communication openings (omitted from the figure). At the central portion of the impeller 20, an engaging hole 20 a is formed that is a nearly D-letter like form in a cross section perpendicular to the shaft direction and that penetrates through the impeller in the thickness direction. The shaft 78 is engaged with in the engaging hole 20 a. Upon energizing the coil of the rotor 77, the shaft 78 rotates so that the impeller 20 rotates.

The casing 18 comprises a combination of the pump cover 14 and a pump body 16. As shown in FIG. 2 and FIG. 5, in an impeller-side face of the pump cover 14 (that is, its lower-side face in FIG. 1), a concave portion 14 a is formed that is circular in planar view. The diameter of the concave portion 14 a is approximately the same as the diameter of the impeller 20, and the depth of the concave portion 14 a is approximately the same as the thickness of the impeller 20.

The impeller 20 is rotatably fitted in the concave portion 14 a.

On a bottom face of the concave portion 14 a of the pump cover 14 (hereinafter, this face may be referred to as lower face of the pump cover), a second pump passage like a groove is formed that extends along a circumference direction in a region facing to the second series of blade grooves 20 c of the impeller 20. An upstream end 31 a of the second pump passage 31 is built near a place facing to an upstream end 30 a of a first pump passage 30 to be described later.

At a downstream end 31 b of the second pump passage 31, a fuel discharge opening 41 is formed.

The fuel discharge opening 41 extends from the second pump passage 31 to an upper face of the pump cover 14 (upper face in FIG. 1), to thereby communicate between the second pump passage 31 and the outside of the casing 18 (in exact detail, the inside of the housing 72).

Between the impeller 20 and the concave portion 14 a of the pump cover 14, a little clearance A in the shaft direction shown in FIG. 6 is formed, and between the impeller 20 and an inner circumference face 14 b of the concave portion 14 a of the pump cover 14, a little clearance B in a radial direction shown in FIG. 6 is formed. These clearances A and B are provided in order for the impeller 20 to rotate smoothly.

It is noted that, although the clearances between the impeller 20 and the pump cover 14 in the figure are shown schematically to be too wide, they are actually fallen in the degree of from several micrometers to several tens micron meters.

On an upper face of the pump body 16, a first pump passage 30 like a groove is formed that extends along a circumference direction in a region facing to the first series of blade grooves 20 b of the impeller 20. At the upstream end 30 a of the first pump passage 30, a fuel suction opening 40 is provided. In between the upstream end 30 a and a downstream end 30 b of the first pump passage 30, a vapor vent hole 30 c is formed that penetrates up and down (up and down in FIG. 1) through the pump body 16. At the central portion of the pump body 16, a concave place 16 b is formed, and in the concave place 16 b, a thrust bearing 33 is disposed in the same axis as the shaft 78.

The thrust bearing 33 receives and bears the thrust load of the rotor 76.

The casing 18 comprised of the pump cover 14 and the pump body 16 is fixed to the housing 72 by caulking inwardly a lower end 72 b of the housing 72, in a state where the impeller 20 is embedded in the concave portion 14 a of the pump cover 14.

Meanwhile, in a state of the casing 18 fixed to the housing 72, the lower end portion 78 b of the shaft 78 is being inserted and fitted in the engaging hole 20 a of the impeller 20 at a location lower than the location where being supported by the bearing 82. Between the lower end of the shaft 78 and the pump body 16, the thrust bearing 33 is interposed.

According to the fuel pump 10 configured as described above, when a current flows through the rotor 76 so that the impeller 20 rotates, the fuel in a fuel tank (omitted from the figures) is sucked in the casing 18 through the fuel suction opening 40. The fuel sucked in the casing 18 firstly flows in the upstream end 30 a of the first pump passage 30. As shown in FIG. 6, the fuel having flowed in the first pump passage 30 forms a swirling flow S between the first pump passage 30 and the first series of blade grooves 20 b by the rotation of the impeller 20, to thereby be pressurized. Further, the fuel having flowed in the first pump passage 30 flows along the first pump passage 30 from the upstream end 30 a toward the downstream end 30 b while being pressurized by the rotation of the impeller. Then, the fuel discharged to the motor section 70 from the fuel discharge opening 41 formed at the downstream end of the second pump passage 31, flows inside the motor section 70, and then discharged to the outside of the fuel pump 10 from the discharge port 73 a formed on the motor cover 73.

The aforementioned little clearance A in the shaft direction shown in FIG. 6, is one of the factors that largely affect the discharge performance of the fuel pump 10. That is, when the clearance becomes broader, the swirling flow S is impaired from flowing smoothly and at the same time, a leakage loss in the casing 18 becomes increased, which results in reduction of the discharge amount of fuel discharged from the fuel discharge opening 41. Namely, keeping and controlling the clearance as little as possible, is an extremely important issue for keeping the discharge performance of the pump. Meanwhile, the impeller 20, which is made of a thermosetting or thermoplastic resin or like resin material, is known to cause its dimensional change (swelling) due to moisture absorption because the impeller 20 is generally used in its immersed state in the fuel as described above, at all times.

When an amount of swelling due to moisture absorption becomes close to the clearance A formed in the shaft direction, the rotational abrasion resistance becomes increased because the rotating motion is obstructed by an interference between the impeller and the casing, thereby causing reduction in the discharge efficiency of the fuel pump. If the impeller 20 further swells beyond the set clearance A, there is a concern that the pump chamber results in its locking in the worst case. In such a background, it is necessary to set and control the clearance to be little to the extent of not causing the locking etc., in expectation of the impeller's swelling due to immersion in the fuel.

The impeller 20 with a shape having an outer ring portion 20 g as shown in FIG. 3, and in particular, made of a thermosetting resin, has a characteristic that the swelling amount at a blade portion 20 f is larger than those at the other portions (a planar portion, the outer periphery portion 20 e). In Embodiment 1, the above characteristic is focused, so that, on a portion of each slidable face inside the casing 18, that is facing to the blade portion 20 f of the impeller, a recessed shape is formed that incorporates an expected swelling amount in advance.

Specifically, with respect to the pump passages 30,31 in nearly C-letter like shape formed on the slidable faces of the pump body 16 and the pump cover 14, the recessed shapes 35,36 in a micron order each incorporating an expected swelling amount of the impeller 20 are formed along the lines extending from these passages in the circumference direction, in other words, in seal portions provided between the upstream end 30 a and the downstream end 30 b and between the upstream end 31 a and the downstream end 31 b of the pump passages 30 and 31, respectively, so that the clearances are partially enlarged.

According to the fuel pump of Embodiment 1 of the invention configured as described above, even when the blade portion 20 f swells, it is possible to prevent increase in rotational resistance of the impeller 20 or occurrence of trouble in the pump chamber, such as locking. At the same time, since the region where the clearance is enlarged is limited to a necessary region, there is no large reduction in pump-discharge performance; namely, it is possible to achieve both ensuring the reliability and keeping the pump performance.

It is noted that the foregoing description is given to the case where the recessed shapes 35,36 formed on the inner faces of the casing 18, are formed on the pump body 16 and the pump cover 14, respectively; however, the recessed shape may be formed on only either one of them.

Further, when recessed shapes 50 a,50 b each incorporating an expected swelling amount are formed, contrary to the foregoing embodiment, on the impeller side as shown in FIG. 6, a similar effect can be expected.

Further, in the fuel pump 10 of the foregoing Embodiment 1, since the recessed shapes are formed only on the pump body 16 and the pump cover 14, or on the impeller 20, it is possible to use conventional components (parts) for the other portions.

Although specific examples of the invention have been detailed using Embodiment 1 as described above, they are merely examples and do not limit the scope of the claims. The technologies described in the claims include various modifications or alternations of the specific examples that are exemplified above.

Moreover, the technical components described in the present description or the drawings exert technical usefulness solely or in various combinations, and should not be limited to the combinations described in the claims at the time of filing of this application. Further, the technologies exemplified in the present description or the drawings can accomplish a plurality of objectives at the same time, and are said to have a technical usefulness simply by achieving one of the objectives.

INDUSTRIAL APPLICABILITY

The invention is well-suited to be applied to a fuel pump for supplying a fuel in a fuel tank to an internal combustion engine (for example, a vehicle engine etc.,)

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   -   10: fuel pump, 12: pump section, 14: pump cover, 16: pump body,         18: casing, 20: impeller, 20 b: first series of blade grooves         (series of recesses), 20 c: second series of blade grooves         (series of recesses), 30,31: pump passages, 30 a: upstream end         of the pump passage 30, 30 b: downstream end of the pump passage         30, 31 a: upstream end of the pump passage 31, 31 b: downstream         end of the pump passage 31, 35: recessed shape (pump-body side),         36: recessed shape (pump-cover side), 40: fuel suction opening,         41: fuel discharge opening, 50 a,50 b: recessed shapes (impeller         side), 70: motor section, 72: housing, 73: motor cover, 74,75:         magnets, 76: rotor, 78: shaft. 

1. A fuel pump (10) which includes an impeller (20) in a disc-like shape; a casing (18) comprising a pump cover (14) and a pump body (16) that rotatably accommodate the impeller; and a motor section (70) that drives to rotate the impeller, wherein, on each of front and back faces of the impeller (20), a series of recesses (20 b,20 c) being repeated in a circumferential direction is formed in a region that extends along the circumferential direction with a given distance apart inside from an outer periphery, wherein, on the pump cover (14) facing to the front face of the impeller, a first groove (31) is formed that extends in a region facing to the series of recesses (20 c) of the impeller, from an upstream end (31 a) to a downstream end (31 b), wherein, on the pump body (16) facing to the back face of the impeller, a second groove (30) is formed that extends in a region facing to the other series of recesses (20 b) of the impeller, from an upstream end (30 a) to a downstream end (30 b), wherein, in the casing (18), there are formed a fuel discharge opening (41) that communicates between near the downstream end (31 b) of the first groove (31) and an outside of the casing (18), and a fuel suction opening (40) that communicates between near the upstream end (30 a) of the second groove (30) and an outside of the casing (18), and wherein, seal portions are provided, as viewed in a rotating direction of the impeller, between the upstream end and the downstream end of the first groove (31) on the pump cover (14) and between the upstream end and the downstream end of the pump body (16), respectively, said fuel pump characterized in that, on at least one of the seal portions of the casing (18) and in its place facing to the series of recesses (20 b,20 c) of the impeller, a recessed shape (35,36) in a micron order is formed in expectation of a swelling amount of said series of recesses (20 b,20 c) of the impeller (20).
 2. The fuel pump of claim 1, characterized in that, on each of the pump cover (14) and the pump body (16), the recessed shape (35,36) is formed.
 3. The fuel pump of claim 1, characterized in that the series of recesses (20 b,20 c) of the impeller (20) is shaped in a recessed shape (50 a,50 b) in expectation of the swelling amount thereof.
 4. A fuel pump (10) which includes an impeller (20) in a disc-like shape; a casing (18) comprising a pump cover (14) and a pump body (16) that rotatably accommodate the impeller; and a motor section (70) that drives to rotate the impeller, wherein, on each of front and back faces of the impeller (20), a series of recesses (20 b,20 c) being repeated in a circumferential direction is formed in a region that extends along the circumferential direction with a given distance apart inside from an outer periphery, wherein, on the pump cover (14) facing to the front face of the impeller, a first groove (31) is formed that extends in a region facing to the series of recesses (20 c) of the impeller, from an upstream end (31 a) to a downstream end (31 b), wherein, on the pump body (16) facing to the back face of the impeller, a second groove (30) is formed that extends in a region facing to the other series of recesses (20 b) of the impeller, from an upstream end (30 a) to a downstream end (30 b), wherein, in the casing (18), there are formed a fuel discharge opening (41) that communicates between near the downstream end (31 b) of the first groove (31) and an outside of the casing (18), and a fuel suction opening (40) that communicates between near the upstream end (30 a) of the second groove (30) and an outside of the casing (18), and wherein, seal portions are provided, as viewed in a rotating direction of the impeller, between the upstream end and the downstream end of the first groove (31) on the pump cover (14) and between the upstream end and the downstream end of the pump body (16), respectively, said fuel pump characterized in that the series of recesses (20 b,20 c) of the impeller (20) is shaped in a recessed shape (50 a,50 b) in expectation of a swelling amount thereof. 